Method of forming improved apertured films by using fluid perforation

ABSTRACT

An apertured film for use as a topsheet in absorbent products wherein the film is apertured and includes a plurality of micro-holes and a plurality of large-sized holes. A method of forming the film is disclosed, as well as an absorbent product incorporating the apertured film as a topsheet. The method includes the step of supporting the starting film on a backing member which has recessed zones into which the film may be deformed. In the preferred embodiment, fluid in the form of columnar streams is directed from at least two sets of orifices against the upper surface of the starting film. The orifices of the first set have a diameter greater than 10 mils, and the orifices of the second set have a diameter less than or equal to 10 mils. The fluid is discharged from the smaller orifices at a pressure of at least 500 psig, and the fluid is discharged from the larger orifices at a pressure less than 500 psig.

FIELD OF THE INVENTION

This invention relates to apertured films having primary utility as acover member for an absorbent article, and to methods and apparatus forforming such apertured films.

BACKGROUND OF THE INVENTION

For many years it has been common to use nonwoven fabrics as a covermember, or facing layer, for products that are adapted to receive bodydischarges, such as disposable diapers, sanitary napkins, adultincontinent devices, wound dressings and the like. Such fabrics havetypically been formed by air-laying, carding, spun bonding and the like,and it is known to post-treat such fabrics to provide strength andintegrity, as by the application of binders or fiber entanglement,either mechanically or by the application of fluid forces. Since suchfabrics are often formed of hydrophobic material, it is also known topost-treat such fabrics with surface active agents to promote thepassage of body discharges through the fabric. Such fabrics have, or areperceived to have, desirable characteristics such as breathability,drapeability, softness, and pleasant hand and tactile impression.

One of the drawbacks associated with facing layers formed of a nonwovenfabric is that liquid such as urine, menses, wound exudates, and thelike that passes through the facing layer and into the absorbent corehas a tendency to strike back through the facing layer, particularlyunder pressure and when the liquid in the absorbent core approaches thevolumetric storage capacity of the core. For this reason, and otherreasons, it has been known in the past to utilize apertured plasticfilms as the facing layer in absorbent articles.

The following list includes disclosures of such apertured films inissued U.S. and foreign patents and published patent applications.

U.S. Pat. No. 3,632,269-Doviak et al.

U.S. Pat. No. 3,929,135-Thompson et al.

U.S. Pat. No. 4,324,246-Mullane

U.S. Pat. No. 4,351,784-Thomas et al.

U.S. Pat. No. 4,381,326-Kelly

U.S. Pat. No. 4,456,570-Thomas et al.

U.S. Pat. No. 4,535,020-Thomas et al.

U.S. Pat. No. 4,690,679-Mattingly et al.

U.S. Pat. No. 4,839,216-Curro et al.

U.S. Pat. No. 4,950,264-Osborn

U.S. Pat. No. 5,009,653-Osborn

U.S. Pat. No. 5,112,690-Cohen et al.

U.S. Pat. No. 5,342,334-Thompson et al.

U.S. Pat. No. 5,352,217-Curro

U.S. Pat. No. 5,368,910-Langdon

U.S. Pat. No. 5,368,926-Thompson et al.

U.S. Pat. No. 5,376,439-Hodgson et al.

U.S. Pat. No. 5,382,245-Thompson et al.

U.S. Pat. No. 5,382,703-Nohr et al.

U.S. Pat. No. 5,383,870-Takai et al.

U.S. Pat. No. 5,387,209-Yamamoto et al.

EP 0 304 617-Suda et al.

EP 0 432 882 A2-Shipley

EP 0 598 204 A1-Garavaglia et al.

EP 0 626 158 A1-Coles et al.

EP 0 626 159 A1-Taki et al.

EP 0 640 328-Tanaka et al.

JP 3-286762 A-Yamamoto et al.

WO 92/18078 A1-Colbert

WO 93/15701 A1-Turi et al.

WO 94/18926 A1-Perry

WO 94/22408 A1-Langdon

WO 94/28846 A1-Steiger et al.

WO 95/00093 A2-Osborn et al.

While certain of such apertured films have functioned reasonably wellfor their intended purposes, the vast majority of such films have actualand perceived major deficiencies. For example, even though suchapertured films may permit fluid to readily pass therethrough, and mayminimize strike-back of such fluid, such apertured films neverthelesstend to have the appearance, feel and hand of a film, rather than afabric. Such film-like characteristics are considered as a negative bythe consumer, and thus absorbent products with apertured films as afacing layer have not met with widespread consumer acceptance.

Major improvements for apertured film facing layers for absorbentproducts are disclosed in commonly assigned, copending U.S. patentapplication Ser. Nos. 08/417,404 U.S. Pat. No. 5,567,376 and 08/417,408abandoned to Turi et al. filed Apr. 5, 1995 as a continuation and adivision of Ser. No. 08/004,379 abandoned, filed Jan. 14, 1993 as acontinuation of Ser. No. 07/744,744 abandoned, filed Aug. 14, 1991(corresponding to publication WO 93/15701 A1 on the above list). In theabove-mentioned Turi et al. applications, an apertured film, and methodsand apparatus for forming the film, are disclosed which impart to thefilm physical characteristics like those of nonwoven fabrics. This isaccomplished by supporting a film formed of stretchable thermoplasticpolymeric material on localized support regions of a backing member, anddirecting a fluid in the form of high pressure, small diameter columnarjets against the upper surface of the film, so that unsupported portionsof the film are directed downwardly between the support regions to causethe formation of micro-holes and fiber-like elements (fibrils)thereabout to impart to the apertured film physical characteristics ofappearance, softness, feel and hand, like those of a nonwoven fabric.While such apertured films are a marked improvement over prior artapertured films, it is desired to provide further improvements in suchapertured films, as by improving the ability of such films to passviscous fluids, such as menses.

For use of apertured films as topsheets for sanitary napkins, clean-dryproperties are very much desired. This means that the sanitary napkinshould appear clean and dry to the user even after it has accepted aflow of menstrual fluid. There are many factors affecting the clean-dryproperties of a sanitary napkin, including the aperture characteristicsand open area of the napkin cover material. There is a trade-off in theeffects of the film aperture size and open area on clean-dry properties.On the one hand, large apertures allow the fluid to be more rapidlytransmitted to the absorbent core. On the other hand, apertures that aretoo large permit the fluid to be transported back through the topsheetfrom the absorbent core (a phenomenon sometimes referred to as "strikeback") and to contact the wearer. Furthermore, large open areas tend toallow the stain on the absorbent core of the napkin to be visiblethrough the topsheet and give the wearer the perception that the producthas not kept her clean. To exhibit both clean and dry properties, atopsheet must have a carefully balanced combination of aperture size andopen area: large enough apertures to rapidly accept a flow of menstrualfluid and to allow it to pass through to the napkin's absorbent core,but small enough to mask the stain on the underlying absorbent core togive the wearer the perception of cleanliness.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, apertured filmsof the type disclosed in the above-mentioned Turi et al. patentapplications are improved by providing such films with larger aperturesand a sufficient open area so that viscous fluids, such as menses, canflow readily through the film. These improved properties are imparted tothe film by subjecting the film to fluid forces in the form of columnarstreams or jets from at least two sets of orifices, the orifices of oneset having a diameter greater than ten mils, and the fluid supplied tothe orifices having a relatively low pressure less than about 500 psig,and the orifices of at least one other set having a diameter of lessthan or equal to ten mils and the fluid supplied thereto having arelatively high pressure greater than about 500 psig. The presentinvention can be practiced with selective variation of the sequence towhich the film is subjected to fluid forces from the low and highpressure orifices, that is, first low pressure then high pressure, orfirst high pressure then low pressure, or other combinations orvariations.

The apertures are, for the most part, irregular in shape and size. Theyare measured by various techniques that approximate the diameter, whichmay be expressed as equivalent hydraulic diameter (EHD) or equivalentcircular diameter (ECD). The resulting apertured film has a combinationof large sized apertures having average EHD's of from about 7 mils toabout 30 mils, and small sized apertures having average EHD's of fromabout 1 mil to about 7 mils. Such apertured films have an open area inthe range of from about 3% to about 13%.

The improved apertured film of the present invention is preferablyformed on a backing member like that shown in FIGS. 17-19 of theabove-mentioned Turi et al. applications, which results in the filmhaving a series of generally parallel ridges formed by generallyvertically oriented side walls which define a series of generallyparallel valleys. The film thus includes generally parallel alternatingsolid or closed portions of the film separated by apertured or openportions of the film, that contain the aforementioned combination oflarge and small sized apertures. Both size apertures are formed as aresult of elongating and drawing the stretchable material between thelocalized support regions of the backing member as a result of theapplication of fluid pressure, and as the film elongates it undergoesthinning until it finally reaches the point of rupturing (i.e.,splitting and fibrillating) to form the above-mentioned apertures.

As with apertured films disclosed in the Turi et al. applications, theapertures are surrounded by a network of fiber-like elements ormicro-strips of drawn plastic material. Such drawn fiber-like elements(fibrils) cooperate with the apertures to provide the apertured filmwith physical characteristics similar to those of nonwoven fabrics. Thefiber like elements have lengths varying from about 0.005 inch (0.013cm) to about 0.05 inch (0.127 cm), widths ranging from about 0.001 inch(0.003 cm) to about 0.035 inch (0.089 cm), and thicknesses ranging fromabout 0.00025 inch (0.0006 cm) to about 0.002 inch (0.005 cm).

In accordance with the present invention, apertured films of the typedisclosed in the above mentioned Turi et al. applications are modifiedso as to provide the film with improved fluid distribution properties inthe region of the film which have been subjected to stretching, bydownward deflection of the film into the recessed region of the supportmember, during formation of the film.

The method for forming an apertured film from a stretchablethermoplastic polymeric material in accordance with the inventioncomprises the steps of providing a starting film comprising saidstretchable thermoplastic polymeric material and having an upper surfaceand a lower surface. A backing member comprising localized supportregions for supporting the starting film is provided. The backing memberhas recessed zones into which the film may be deformed by theapplication thereto of fluid forces. Means for allowing said appliedfluid to be transported away from the backing member are provided.

The starting film on the backing member has portions of the lowersurface of the film being in contact with the support regions of thebacking member. The upper surface of the film faces away from thebacking member.

A fluid in the form of columnar streams from at least two sets oforifices is directed against the upper surface of the starting film in azone of contact, i.e., a zone in which the film is subjected to theforces from the fluid streams. The orifices of the first set each have adiameter greater than ten mils and the fluid supplied thereto has apressure less than 500 psig. to cause the formation of large sized holesin said starting film. The orifices of the second set each have adiameter less than or equal to ten mils and the fluid supplied theretohas a pressure of at least 500 psig. to cause the formation ofmicro-holes in the starting film.

The film is removed from the contact zone, and the now-apertured film isremoved from the backing member.

Other features and advantages of the present invention will becomereadily apparent from the following detailed description, theaccompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side elevational view of a production line forforming apertured film in accordance with the present invention;

FIG. 2 is a schematic side elevational view, on an enlarged scale, ofthe unwind section of the apparatus for producing the apertured film ofthe present invention;

FIG. 3 is an enlarged side elevational view of the aperturing section ofthe apparatus used to form the apertured film of the present invention;

FIG. 4 is an enlarged side elevational view of the dewatering section ofthe apparatus used to form the apertured film of the present invention;

FIG. 5 is an enlarged side elevational view of the drying section of theapparatus used to form the apertured film of the present invention;

FIG. 6 is an enlarged side elevational view of the slitter/rewindersection of the apparatus used to form the apertured film of the presentinvention;

FIG. 7A is a schematic view of an orifice strip used in the apparatus toform one of the apertured films of the present invention;

FIGS. 7B, C, D and E are enlarged views of orifice patterns which can beused in the apparatus to form the apertured films of the presentinvention;

FIG. 8 is an exploded perspective view of a starting film positioned ona backing member for processing in accordance with the presentinvention;

FIG. 9 is a top plan view of the backing member shown in the lowerportion of FIG. 8;

FIG. 10 is an enlarged cross-sectional view taken along line 10--10 ofFIG. 9;

FIGS. 11A, B, C, D are views similar to FIG. 10 showing sequentialstages in the drawing of the starting film to form apertures inaccordance with the teachings of the present invention;

FIG. 12 is a photograph in top plan of an apertured film formed inaccordance with the present invention at a magnification of 7.5 times;

FIG. 13 is an end elevational view of the apertured film of FIG. 12;

FIG. 14 is an end elevational view of the apertured film of FIG. 12 at amagnification of 15 times;

FIG. 15 is a top plan view of another apertured film formed inaccordance with the teachings of the present invention at amagnification of 7.5 times;

FIG. 16 is an end elevational view of the apertured film of FIG. 15;

FIG. 17 is an end elevational view of the apertured film of FIG. 15 at amagnification of 15 times;

FIGS. 18A and B are photographs taken at a magnification of 10× ofapertured film formed in accordance with the invention, formed from anembossed starting film having the female side thereof against theassociated forming member, wherein the film was subjected to aperturingby a sequence of three orifice strips, the first having relatively largeorifices in accordance with FIG. 7D, and the second and third havingrelatively small orifices in accordance with FIG. 7A (FIG. 18A being theside thereof against which the water jets were directed, FIG. 18B beingthe side thereof positioned against the associated forming member);

FIGS. 18C and D are photographs taken at a magnification of 10× ofapertured film formed in accordance with the invention, formed from anembossed starting film having the female side thereof against theassociated forming member, wherein the film was subjected to aperturingby a single orifice strip having relatively large orifices in accordancewith FIG. 7D (FIG. 18C showing the side thereof against which the waterjets were FIG. 18D showing the side thereof positioned against theassociated forming member);

FIG. 19 is a block diagram showing the various steps of the process forproducing the apertured film in accordance with the present invention;

FIG. 20 is a perspective view of a sanitary napkin comprised of anapertured film according to the present invention; and

FIG. 21 is a view, partially in section, taken along line 21--21 of FIG.20;

FIG. 22 is a graph depicting aperture size distribution in a sample ofapertured film made at 875 psig. on an apparatus using three orificestrips each having a plurality of orifices, all of the orifices being 5mils in diameter;

FIG. 23 is a graph depicting aperture size distribution in a sample ofapertured film made on an apparatus comprising a single orifice striphaving a plurality of orifices each 20 mils in diameter, said orificestrip being shown in FIG. 7C;

FIG. 24 is a graph depicting aperture size distribution in a sample ofapertured film made on an apparatus comprising a first orifice strip(shown in FIG. 7C) having a plurality of orifices, all of which have adiameter of 20 mils, and a second orifice strip, downstream of the firststrip, wherein the second strip (shown in FIG. 7A) has a plurality oforifices all of which have a diameter of 5 mils;

FIG. 25 is a graph depicting aperture size distribution in a sample ofapertured film made in accordance with the invention; and

FIG. 26 is a graph depicting the results of comparison in which thespacing of the orifices comprising the orifice strip is varied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describedpresently preferred embodiments, with the understanding that the presentdisclosure is to be considered as an exemplification of the invention,and is not intended to limit the invention to the specific embodimentsillustrated.

Referring now to the drawings, FIG. 1 is a schematic, side elevationalview of one embodiment of a production line that may be utilized toproduce apertured films in accordance with the teachings of the presentinvention. As is indicated by the direction arrow, the process flowproceeds from right to left in FIG. 1. As is shown in FIG. 1, theproduction line has five major stations; a film unwinding station 30, anaperturing station 40, a dewatering station 50, a drying station 60, anda slitting, rewinding, and surfactant application station 70.

As shown in FIG. 2 in the film unwinding station, two rolls 31 ofstarting film material 33 are mounted for rotation on frame F. The filmfrom rolls 31 is fed over guide rollers and into festoon 32 which has anautomatic (closed loop) tension control system. Film 33, under suitabletension, e.g., between 0.1 to 1 pound per linear inch, emerges fromfestoon 32, and proceeds to the aperturing station 40.

While many different starting film materials are suitable for use in thepresent invention, one of the preferred materials is a polyethylene filmcommercially available from Exxon Chemical under product designationEMB-631. This film is an embossed, white pigmented polyethylene film.The polyethylene component consists of a blend of 40% by weight lowdensity polyethylene and 60% by weight linear low density polyethylene.The film has 6.5% by weight titanium dioxide.

The starting film is embossed with a diamond pattern at 165 lines perinch to provide on one side of the film, referred to as the male side, aplurality of discontinuous observable protrusions separated by acontinuous, interconnected grooved pattern. The other side of theembossed starting film, referred to as the female side, has a pluralityof observable, cupped recesses separated by a continuous, interconnectedrib pattern. The cupped recesses in the female side of the film are inrespective registration with the protrusions on the male side of thefilm. The starting film is electrostatically treated with a coronadischarge treatment on one side, preferably the male side. The film hasan ultimate tensile strength of 1750 grams in the machine direction(with 500% elongation at break), and 1300 grams in the cross direction(with 650% elongation at break), as determined using ASTM test D-882.

The process for making the film of the invention may be either batch orcontinuous, generally similar to the batch and continuous processesdisclosed in co-pending Ser. No. 08/417,404 U.S. Pat. No. 5,567,376. Thepreferred embodiment is a continuous apparatus, as further disclosedherein.

With reference to FIG. 3, the film 33 from the unwind station is shownentering aperturing station 40 at the right hand side thereof.Aperturing station 40 includes a honeycomb-type support drum 41rotatably mounted on a frame F1. The drum 41 has a three-dimensionalbacking or forming member, described in detail hereinafter, mounted onits outer peripheral surface. Four water jet manifolds 42 are alsosupported on frame F1 and four suction slots, one for each manifold 42,are provided interiorly of the support drum, as is also hereinafterdescribed in detail. The suction slots are mounted within the drum andare aligned with the water jet manifolds located outside of the drum.Each water jet manifold comprises a metallic strip, hereinaftersometimes referred to as an orifice strip, having a plurality oforifices having predetermined size and spacing. Specific examples ofsuch orifice strips are described in more detail hereinafter. A givenmanifold 42 may comprise one or more orifice strips. The orifice sizepreferably remains constant for each strip. However, the orifice sizemay vary on a given strip. The distance between the lower surface of theorifice strip and the outer surface of the backing member of theaperturing drum is preferably in the range of between 0.50 to 1.0inches.

Hot water under pressure is pumped to the manifolds 42, and thepressurized water exits through the plurality of orifices in the orificestrip in the form of columnar water jets. The water pressure in eachmanifold 42 may be separately regulated. The entering film 33 is trainedover a guide roller 43, and then over the outer periphery of the threedimensional forming member mounted over the support drum 41. Thecolumnar streams of water exiting the orifice strips impinge on the filmand cause the film to deflect downwardly into the recessed regions ofthe backing member mounted on the support drum, thereby causing the filmto stretch and rupture into a multiplicity of irregular size holes. Thenow-apertured film 44 emerges from aperturing station 40 at theleft-hand side thereof and passes to dewatering section 50.

As is shown in FIG. 4, in the dewatering section 50, two dewateringdrums 51 are mounted for rotation on frame F3. Drums 51 have a honeycombconfiguration, and each drum has two vacuum slots associated therewith,capable of drawing vacuum up to 7 inches Hg. Twelve air knives 52 areprovided, six air knives being provided for each drum 51. The suctionslots associated with the dewatering drums 51 are located internally ofthe drums, whereas air knives 52 are located outside of the drums 51.Excess water is removed from the apertured film by the impingement ofhigh velocity air from knives 52 and by suction through the suctionslots in drums 51. Air knives 52 operate at an air temperature rangebetween about 150°-180° F. Total air flow through the twelve air knives52 is between about 1,000 to about 2,000 cubic feet per minute perlinear foot of apertured film width. The dewatered film 53 emerges fromthe dewatering station 50, at the left-hand side thereof, and passes tothe drying section.

With reference to FIG. 5, the air drying station 60 is illustrated asincluding two vacuum drums 61 mounted on frame F4. Each drum 61 has asuction slot, which has an arc of 300° around the drum. Twenty airknives 62 are positioned outwardly of each vacuum drum 61 and the airknives 62 operate at a temperature between 150°-180° F. The combined airflow for all forty air knives 62 is between about 5,000 to about 7,000cfm per linear foot of apertured film width. The pressure drop caused bythe vacuum in drums 61 is about 2 inches of water measured across thefilm. The dried film 63 emerges from drying section 60 at the left-handside thereof and passes to slitter/rewinder section 70.

Referring now to FIG. 6, the film 63 from the drying section enters theslitter/rewinder station 70 at the right hand side thereof. A slitter71, consisting of spaced score cut type slitting knives, cuts the driedapertured film to the desired width. The dried and slit apertured filmthen passes to a surfactant applicator 72, where a suitable surfactant,e.g., Tween 20, is applied to the film by kiss-coating. The surfactantis preferably provided in an aqueous solution consisting of about48.8±1.5 percent surfactant. In an exemplary embodiment of theinvention, the surfactant roller coating speed is 15±3 inches perminute. Preferably, the surfactant is applied to the male side of thefilm. The above-mentioned parameters result in a surfactant solutionadd-on of 0.25 mg/in² ±0.07.

Referring to FIGS. 7A-7E, the columnar jets of water are discharged fromone or more orifice strips having a plurality of orifices. Preferably,the orifices are formed by drilling a precursor metallic strip to formcylindrical holes. However, it is anticipated that holes of variousshapes may be used.

FIG. 7A shows an orifice strip 80 for delivering columnar jets of watereach having a relatively small cross-section to form micro-holes in thefilm. The orifices 82 in the manifold have a diameter of 5 mils (0.005inch), and are spaced 0.020 inch apart. This manifold strip is availablefrom the Nippon Nozzle Co., of Kobe, Japan.

FIGS. 7B-7E show orifice strips for producing columnar jets of water,each having a relatively large cross section, to form large sized holesin the film. FIG. 7B shows an orifice strip having two rows 84, 86 oforifices 84', 86' that are spaced apart on opposite sides of a centertangent line. The orifices in each row have a diameter of 15 mils (0.015inch), and are spaced 0.022 inch apart, center-to-center. The spacing ofthe orifices in the top row is offset from the spacing of the orificesin the bottom row by 0.011 inch. The strip contains 90.9 orifices perinch.

FIG. 7C shows an orifice strip having two rows 88, 90 of orifices 88',90' that are spaced apart on opposite sides of a center tangent line.The orifices in each row have a diameter of 20 mils (0.020 inch), andare spaced 0.032 inch apart. The spacing of the orifices in the top rowis offset from the spacing of the orifices in the bottom row by 0.016inch. The strip contains 62.5 orifices per inch.

FIG. 7D shows an orifice strip having two rows 92, 94 of orifices 92',94' that are spaced apart on opposite sides of a center tangent line.The orifices in each row have a diameter of 25 mils (0.025 inch), andare spaced 0.038 inch apart. The spacing of the orifices in the top rowis offset from the spacing of the orifices in the bottom row by 0.019inch. The strip contains 52.6 orifices per inch.

FIG. 7E shows an orifice strip for delivering columnar jets of watereach having a relatively large cross-section for forming large sizedholes in film. The orifices each have a diameter of 0.025 inches, andare spaced 0.083 inches, center-to-center. While the orifice strip shownin FIG. 7E is suitable for forming film in accordance with the presentinvention, use of orifice strips such as shown in FIG. 7B-7D ispresently preferred for use in combination with one or more orificestrips having relatively small orifices for formation of micro-sizedholes.

The small orifices (see FIG. 7A) preferably have a diameter under 10mils. The larger orifices (see FIGS. 7B-7E) preferably have a diametergreater than 10 mils.

An apparatus for making apertured films of the present invention isdescribed in detail in co-pending patent application Ser. No.08/417,404. The apparatus for making the film of the present inventioncontains certain additional features, including a second set of orificestrips as discussed above with reference to FIGS. 7B-7E. The pressure ofthe water delivered to the small orifices is generally greater than 500psig, preferably on the order of 500-1600 psig or higher. The pressureof water delivered to the large orifices is generally less than 500psig, preferably on the order of 125-200 psig.

In a preferred embodiment, the aperturing equipment consists of ahoneycomb type support drum, a three dimensional forming member, severalwater jet manifolds, and corresponding suction slots arranged interiorlyof and sequentially along a section of the circumference of the drum.The forming member is an engraved sleeve, as shown in FIGS. 8-10, whichis mounted onto the honeycomb support drum. The suction slots aremounted within the drum and they are lined up with the water jetmanifolds located outside the drum. Each water jet manifold contains ametallic strip having a plurality of orifices. For a given manifold, theorifice size remains constant throughout the strip. The distance betweenthe orifice strip and the surface of the engraved sleeve is preferablybetween 0.50 to 1 inch. The manifolds are pressurized by pumping inheated water. The pressurized water exits through the series of orificesin the orifice strip, thus creating substantially columnar water jets.The energy of the columnar hot water jets impinging on the film causesthe film to contour toward the surface of the engraved sleeve therebycausing the film to stretch and rupture into a multiplicity of irregularsize holes. The pressure and temperature of the water supplied to eachmanifold may be separately regulated. The process parameters are asfollows:

Line Speed (yards/min): 50-200

Water Temperature: 155°-165° F.

Maximum Number of Manifolds Used: 3

Distance between Manifold Strip and Surface of Sleeve: 0.50"-1"

Low Pressure Manifold:

Number of Manifolds: 1

Orifice Size Range (inch): 0.0145 to 0.030

Pressure (psig): 150±25

Water Flow: 8.0±2.0 gallons per minute per inch of orifice strip(gpm/in)

Suction Slot Vacuum (inch of Hg): 5.0±2.0 (-17±10.2 kPa)

High Pressure Manifold:

Number of Manifolds: Maximum of 2

Orifice Size Range (inch): 0.005 to 0.007

Pressure (psig): 1,150±350

Water Flow: 0.9±0.22 gallons per minute per inch of orifice strip

Suction Slot Vacuum (inch of Hg): 5±3 (-17±10.2 kPa)

Manifold Usage Sequence:

The pressurized water jet manifolds and their associated orifice stripscan be arranged in a variety of sequences relative to the direction ofcontinuous travel of the film on the drum. Any of the following fivesequences may be used to aperture the film:

1. Low Pressure, High Pressure

2. Low Pressure, High Pressure, High Pressure

3. High Pressure, Low Pressure

4. High Pressure, Low Pressure, High Pressure

5. High Pressure, High Pressure, Low Pressure

Referring to FIGS. 8-10, the forming member is a three dimensionalsurface having a plurality of radially extending support elements thatrise from the base of the forming or backing member. These elements aresubstantially similar to the corresponding elements disclosed inco-pending patent application Ser. No. 08/417,404 U.S. Pat. No.5,567,376.

FIG. 8 is an exploded perspective view of starting film 100 supported onbacking member 102. The starting film may be either embossed orunembossed. Alternatively, a portion 104 of starting film 100 comprisesembossments 106, and unembossed regions 108 as shown in the upperportion of FIG. 8.

Backing member 102 comprises a base portion 110 having an upper surface110a and a lower surface 110b. Backing member 102 further comprises aplurality of apertures 112 running through the thickness of base 110from upper surface 110a to lower surface 110b. As will be seenhereinafter, apertures 112 are provided to allow for removal of waterduring the manufacture of apertured film according to the invention.Backing member 102 also includes a plurality of radially-extendingsupport elements 114. These support elements comprise a base 116coinciding with the plane of upper surface 110a of portion 110 and apair of angled side walls 118, 120 (best seen in FIGS. 9 and 10). Sidewalls 118, 120 extend outwardly from base 116 to meet at a land portionor ridge 122. Support elements 114 are aligned in parallel and spacedequidistantly from one another. They may run either parallel to,perpendicular to, or at any angle to the sides of the backing member. Asshown in FIGS. 8 and 9, these support elements 114, when viewed in plan,are generally sinusoidal-like or wavy in configuration. It will beunderstood that the support elements may be provided in otherconfigurations, e.g., straight-line, zig-zag and the like. A detaileddescription of the forming member is disclosed in co-pending patentapplication Ser. No. 08/417,404 U.S. Pat. No. 5,567,376.

Referring to FIGS. 11A-D, the progression of the drawing of the startingfilm 124 to form apertures in accordance with the teachings of thepresent invention are shown. Referring to FIG. 11A, the starting film124 is initially laid on the backing member. Referring to FIG. 11B, thefilm 124 deforms in response to the application of columnar jets ofwater and is drawn (i.e., stretched) downwardly and partially into thespace between support elements. Referring to FIG. 11C, as the film 124is drawn, it becomes thinner. Referring to FIG. 11D, as the film isfurther drawn and becomes thinner, it begins to break apart and formholes 126. This process is further described in co-pending patentapplication Ser No. 08/417,404 U.S. Pat. No. 5,567,376, wherein theformation of micro-holes surrounded by micro-strips of film material, orfibrils, is described.

Due to the vertical elements on the forming member, the film of thepresent invention is expanded (i.e., is given significant dimensionalityin the z-direction relative to the original thickness of the precursorunapertured film) immediately as it comes off the process. In some priorart processes, expansion in the z-direction must be accomplished in aseparate embossing step (see for example, U.S. Pat. No. 4,609,518). Anexpanded topsheet limits the contact between the wearer and theabsorbent layer and thus enhances the feeling of dryness in productsthat incorporate it.

In the films, absorbent products and methods disclosed herein, the holesin the film include both micro-holes and large sized holes, or mayinclude large sized holes only. It is believed that the micro-holes areformed primarily from the drawing of film material in response toapplication of columnar jets of water coming from the smaller orificesof the orifice strip discussed above. It is believed that the largesized holes, also formed from the drawing of film material, are formedprimarily in response to application of the columnar jets of watercoming from the larger orifices, rather than the smaller orifices, ofthe orifice strip discussed above.

The resulting apertured film has a combination of large sized holes orapertures having average EHD's of from about 7 mils to about 30 mils,and small sized apertures or holes, sometimes referred to as micro-sizedholes, having average EHD's of from about 1 mil to about 7 mils. Suchapertured films have an open area in the range of from about 3% to about13%. It has been found that using orifice strips having orifices whosediameters range from about 10 to 25 mils results in the formation ofapertures in the film having an average EHD of about 7 mils to about 17mils. The fibrils surrounding and defining the micro-holes and the largesized holes are described in detail in co-pending patent applicationSer. No. 08/417,404. The fibrils have lengths ranging from about 0.005inch (0.013 cm) to about 0.05 inch (0.127 cm); widths ranging from about0.001 inch (0.003 cm) to about 0.035 inch (0.089 cm); and thicknessesranging from about 0.00025 inch (0.006 cm) to about 0.002 inch (0.005cm). Photographs in FIGS. 12-18A, B show the combination of micro-holesand large sized holes of an apertured film made in accordance with theinvention. Photographs in FIGS. 18C, D show large sized holes of anapertured film made in accordance with the invention.

The combination of large sized holes and micro-holes of the dimensionsdiscussed above yield an improvement in the clean and dry properties ofthe film when used as a topsheet for a sanitary napkin. The resultingopen area is in the range of 3 to 13%. In the prior art film havingmicro-holes only (see co-pending application Ser. No. 8/417,404 U.S.Pat. No. 5,567,376), when 5 mil diameter columnar jets of water areused, the resulting apertured film has micro-holes with an average EHDof 3 mils, and has an open area of about 3%. The increased aperture sizeand open area in an apertured film having large sized holes incombination with micro-holes in accordance with the invention providesan improved level of aperture size and open area so as to strike anadvantageous balance: large enough apertures to rapidly accept a flow ofmenstrual fluid and to allow it to pass through to the napkin'sabsorbent core, but small enough to mask the stain on the absorbent padto give the consumer the perception of cleanliness. Thus, the absorbentproducts of the present invention made with the apertured films of thepresent invention have much improved clean and dry properties.

In a preferred embodiment of the invention, the starting film isapertured by large diameter, low pressure columnar water jets and smalldiameter, high pressure columnar water jets. This combination of jets atboth high and low pressure produces larger apertures and greater openarea than films made with small diameter high pressure jets alone. Filmsmade by this embodiment also appear softer to the user than films madeonly with large diameter, low pressure jets.

FIG. 19 is a block diagram showing the several steps in the process forproducing the novel apertured films of the present invention. The firststep in the process is to position a piece of thin, stretchable film ofthermoplastic polymer material on a backing or support member (Box 1).The support member with the stretchable film thereon is passed underhigh pressure fluid ejecting nozzles (Box 2). The preferred fluid iswater. The water is transported away from the support member, preferablyusing a vacuum (Box 3). The film is de-watered, suction being preferredfor this purpose (Box 4). The de-watered apertured film is removed fromthe support member (Box 5). Residual water is removed from the aperturedfilm, e.g., by applying a stream of air thereto (Box 6). Surfactant isnext applied to the apertured film (Box 7). The apertured film is thenrolled up to await use as is or as a structural component of anotherproduct such as a sanitary napkin, disposable diaper or wound dressing(Box 8).

Referring to FIGS. 20 and 21, there is shown a sanitary napkin 130comprising an absorbent core 132 of wood pulp fibers, a thin,fluid-impermeable barrier film 134 and a covering material 136 which maybe any of the apertured films of the invention. Preferably, the coveringfilm material has the structure shown and described herein. Barrier film134, which may comprise, e.g., a thin film of polyethylene, contacts thelower surface of absorbent core 132 and runs part way up thelongitudinal sides of the absorbent core. Covering material 136 has alength somewhat longer than the length of the absorbent core and iswrapped around the absorbent core and barrier film as shown in FIG. 21.The longitudinal edges of the cover material are overlapped and sealedtogether on the lower surface of the napkin in the usual manner. In theembodiment illustrated, the cover material is sealed to itself at theends 138, 140 of the sanitary napkin. As illustrated in FIG. 21,sanitary napkin 130 has a layer of adhesive 142 for adhering the napkinto the undergarment of the user. Adhesive 142 is protected prior to useby a removable release strip 144.

EXAMPLE 1

In one embodiment of the apertured film in accordance with theinvention, the starting material is an embossed film supplied by ExxonChemical under the designation EMB-631, and having a thickness of 0.95mils. This film is corona discharge treated on its male side. The filmis placed on the forming member shown in FIGS. 8-10 which is mounted ona support drum as described in co-pending applications Ser. Nos.08/417,404 U.S. Pat. No. 5,567,376 and 08/417,408 abandoned to Turi etal. with the corona-treated male side of the film facing away from theforming member. Two manifolds for directing columnar streams of water atthe film were used. The first, or upstream, manifold has the orificeconfiguration shown in FIG. 7D of the drawings, i.e., there are twooffset rows 92, 94 of orifices 92', 94', each of the orifices having adiameter of 0.025 inches. The orifices are spaced a distance of 0.038inches center-to-center to provide a total of 52.6 holes per inch. Thesecond, or downstream, manifold has the orifice configuration shown inFIG. 7A of the drawings, i.e., there is a single row of orifices eachhaving a diameter of 0.005 inches. These orifices are spaced 0.020inches on a center-to-center basis. There is a total of 50 such orificesper inch. Water having a temperature of 165° F. is supplied at apressure of 165 psig to the first manifold, and at a pressure of 1400psig to the second manifold. The film is passed under the manifolds at aspeed of 435 feet per minute. The suction pressure inside the drum isminus 50 inches of water. The film is dewatered with the apparatus shownin FIG. 4 and is dried with the apparatus shown in FIG. 5. Followingdrying, the male side of the film is kiss-coated with a 48.8% solutionof Tween-20 in water to a solution add-on of 0.25 mg/in². Subsequentrolling of the film effects transfer of the surfactant solution from thecorona-treated male side to the female side. After the surfactantsolution ultimately dries, the film has a bulk surfactant add-on(including all surfaces of the film) of 0.12 mg/in². The resultingapertured film has an air permeability of approximately 325 cubic feetper minute per square foot (cfm/ft²) at a pressure differential (ΔP) of0.5 inches of water. The film has a measured open area of 6.24% and anaverage ECD of 10-11 mils. ECD (Equivalent Circular Diameter) is acalculated aperture diameter that is based on a measurement of the areaof the aperture. The area is measured using the disclosed hardware andsoftware for measuring EHD in co-pending patent application Ser. No.08/417,404 now U.S. Pat. No. 5,561,376. The formula for ECD isECD=(4A/π)^(1/2) where A is the measured area of an aperture. There isan average of 500 apertures per square inch. The bulk thickness is 14.5mils.

EXAMPLE 2

Another embodiment of the apertured film of the invention was made usingthe same starting film and forming member as used in Example 1. The linespeed was 50 yds/min. Two manifolds for directing columnar streams ofwater at the film were used. The first, or upstream, manifold has theorifice configuration shown in FIG. 7C of the drawings, i.e., there aretwo offset rows 88, 90 of orifices 88', 90', each of the orifices havinga diameter of 0.020 inches. The orifices are spaced a distance of 0.032inches center-to-center to provide a total of 62.5 holes per inch. Thesecond, or downstream, manifold has the orifice configuration shown inFIG. 7A of the drawings, i.e., there is a single row of orifices eachhaving a diameter of 0.005 inches. These orifices are spaced 0.020inches on a center-to-center basis. There is a total of 50 such orificesper inch. Water having a temperature of 160° F. is supplied at apressure of 150 psig to the first manifold, and at a pressure of 1500psig to the second manifold. The drum had a vacuum of 6 inches of Hg(-20.4 kPa).

In the dewatering section, there were six dewatering knives, and avacuum of 4" of Hg. The air temperature for the first set of air kniveswas 180° F. The air temperature for the second set of air knives was120° F. There were two film drying cylinders and each cylinder had fiveheated air knives. The hot air temperature for the knives was 150° F.,and the vacuum was less than 1" of water.

The apertured film produced according to Example 2 was analyzed bymicroscopy. Open area, hole size distribution and total features (numberof holes) were measured by image analysis techniques, with the followingresults:

    ______________________________________                                        Open Area                                                                             St.     E.H.D.*  ECD           Aperture                               (mean)  Dev.    (mean)   (mean) St. Dev.                                                                             Count                                  ______________________________________                                        6.19%   .68     7.61 mils                                                                              10.85 mils                                                                           10.47 mils                                                                           858/sq.in.                             ______________________________________                                         *EHD is measured as discussed in copending patent application Ser. No.        08/417,404 U.S. 5,567,376, which is incorporated by reference.           

The characteristics of the orifice strips used in the experimentsdescribed below are shown in Table 1:

                  TABLE 1                                                         ______________________________________                                        Characteristics of Orifice Strips                                                           Number Of             Number Of                                 Orifice                                                                             Orifice Rows Of   Intra-Row Spacing                                                                         Orifices Per                              Strip Size    Orifices Per                                                                            Between Orifices                                                                          Strip Per Inch                            ID    (inches)                                                                              Orifice Strip                                                                           (center-to-center, in.)                                                                   Of Orifice Strip                          ______________________________________                                        a     0.005   1         0.020       50                                        b     0.010   2         0.015       133                                       c     0.015   2         0.022       90.9                                      d     0.020   2         0.032       62.5                                      e     0.025   2         0.038       52.6                                      f     0.025   1         0.083       12                                        ______________________________________                                    

Experimentation With Batch Formation Of Films

The batch film aperturing apparatus used in the experiments reported inTable 2 below was similar to that shown in FIG. 3 of the drawings.However, only one water manifold 42 was used, and only one of theavailable vacuum slots was used. Each of the orifice strips labeled "b"through "f" in Table 1 was in turn mounted in the single water jetmanifold and used to make one or more apertured films as shown in Table2. The starting film and forming member were the same as those used inExample 1.

A piece of starting film was mounted to the outer surface of the formingmember by a series of pins projecting from the forming member. Thehoneycomb support drum was rotated so that the mounted film was out ofline with the single orifice strip. Vacuum was applied to the inside ofthe honeycomb support drum. Heated, pressurized water was supplied tothe manifold. The honeycomb support drum motor was rotated to pass thestarting film once under the orifice strip. The resultant film wasremoved from the forming member and air dried. Process conditions usedto make films and the resultant film properties are shown in Table 2below.

                                      TABLE 2                                     __________________________________________________________________________    Batch Film Aperturing Experiments                                                                            Mean                                                                          Equivalent                                                                    Hydraulic                                             Water                                                                             Water      Film Open                                                                              Diameter                                          Orifice                                                                           Pressure                                                                          Temp.                                                                              Vacuum*                                                                             Speed                                                                              Area                                                                              (EHD)**                                        Ex. #                                                                            ID  (psi)                                                                             (°F.)                                                                       (in. Water)                                                                         (ft/min)                                                                           (%)**                                                                             (mils)                                         __________________________________________________________________________     1 b   350 160  60    150  3.6 10.7                                            2 b   550 160  60    150  6.5 10.3                                            3 b   1000                                                                              160  60    150  8.5  7.7                                            4 c   200 160  60    150  2.9 11.7                                            5 c   400 160  60    150  8.7 16.3                                            6 c   550 160  60    150  11.7                                                                              14.3                                            7 c   850 160  60    150  11.5                                                                               8.7                                            8 d   160 160  60    150  1.5 11.1                                            9 d   250 160  60    150  8.1 17.1                                           10 d   350 160  60    150  9.4 14.7                                           11 d   550 160  60    150  13.2                                                                              13.7                                           12 e   150 160  60    150  2.0 10.1                                           13 e   240 160  60    150  7.4 14.9                                           14 e   375 160  60    150  12.8                                                                              17.2                                            14a                                                                             f   150 160  60    150  3.5 13.0 (1)                                        14b                                                                             f   200 160  60    150  5.71                                                                              12.8 (1)                                        14c                                                                             f   250 160  60    150  6.0 11.5 (1)                                       __________________________________________________________________________     *vacuum value is inches of water below atmospheric pressure.                  **Open Area and EHD were measured according to the method disclosed in        copending application Ser. No. 08/417,404, which is incorporated herein b     reference.                                                                    (1) = ECD                                                                

The data indicate the following trends:

Increasing the fluid pressure with an orifice strip of a given sizeincreases open area.

Increasing the orifice diameter increases open area at a given fluidpressure.

Due to stretch of material that occurs during the process of formingapertures, the weight per area of the film is reduced to about 0.47oz/sq.yd, which is 65% of the initial film weight per unit area. Whenthe 0.025 inch diameter orifice strips spaced at 0.038 inch, 0.050 inch,0.062 inch and 0.075 inch of Table 8 were used, the open area decreasedfrom 13.1% to 12.0, 11.2, and 10.1% respectively.

Experimentation With Continuous Formation Of Film

Additional embodiments of films according to the present invention weremade using the starting film, forming member and general procedure ofExample 1. The characteristics of the orifice strips used are describedin Table 1 above. All of the runs were made using water at 160° F., withthe corona treated male side of the starting film facing away from theforming member. The number of orifice strips used, and theircharacteristics and processing conditions are shown in the followingtable:

                                      TABLE 3                                     __________________________________________________________________________    Continuous Film Aperturing Experiments                                               Orifice Strip #1                                                                      Orifice Strip #2                                                                      Orifice Strip #3                                                                       Line                                                 Orifice                                                                           Pressure                                                                          Orifice                                                                           Pressure                                                                          Orifice                                                                            Pressure                                                                          Speed                                         Experiment #                                                                         Strip ID                                                                          (psi)                                                                             Strip ID                                                                          (psi)                                                                             Strip ID                                                                           (psi)                                                                             (ft/min)                                      __________________________________________________________________________    15     d    150                 120                                           16     d    150                                                                              a   1000         120                                           17     d    150                                                                              a   1000                                                                              a    1000                                                                              120                                           18     a   1000                 120                                           19     a   1000                                                                              a   1000         120                                           20     a    875                                                                              a    875                                                                              a     875                                                                              120                                           21     a    875                                                                              a    875                                                                              a     875                                                                              150                                           22     a   1000                                                                              d    150         120                                           23     a   1000                                                                              d    150                                                                              a    1000                                                                              120                                           __________________________________________________________________________

Following air drying, the films were kiss-coated with an aqueoussolution of Tween 20 surfactant at a concentration of 48.8% on thecorona-treated male side to produce a bulk surfactant add-on of 0.12mg/in² of film as described hereinabove in connection with Example 1.

The apertured films produced in these experiments were evaluated for airpermeability, aperture size, open area, strikethrough and bending length(a measure of film stiffness). Tests were run according to the followingmethods well known in the art. Air permeability was tested according toASTM D737. Film aperture size and open area were determined and used tocalculate Equivalent Circular Diameter (ECD). Strikethrough is ameasurement of the time required for 5 cc of a test fluid to be absorbedthrough the film supported on ground fluff wood pulp. The test fluid isa mixture of 75% by weight of defibrinated bovine blood and 25% byweight of a 10% by weight aqueous solution polyvinylpyrrolidone (GAFPovidone K-90). Bending length in the machine direction (MD) and crossdirection (CD) were measured according to ASTM D1388. The properties ofthe film produced in continuous runs are shown in Tables 4-7 below.

                  TABLE 4                                                         ______________________________________                                        Continuous Apertured Film Properties - Air Permeability                                   Air Permeability                                                  Experiment #                                                                              CFM/SQFT @ 0.5 in. H.sub.2 O ΔP)                            ______________________________________                                        15          139.33                                                            16          222.00                                                            17          246.67                                                            18          107.00                                                            19          143.67                                                            20          173.67                                                            21          170.67                                                            22          214.33                                                            23          212.67                                                            ______________________________________                                    

The data in Table 4 show that the combination of large diameter andsmall diameter orifices (experiments 16,17, 22 and 23) produces a morepermeable, open film than films made with small diameter orifices alone(experiments 18-21). It is believed that the use of large diameterorifices, albeit used at lower water pressure, is the primary cause forthe creation of large holes. Further, it is believed that the use ofsmaller diameter orifices is the primary cause for the creation of thesmaller micro-holes.

                  TABLE 5                                                         ______________________________________                                        Continuous Apertured Film Properties - Aperture Size And Open Area                     Average                                                                       Equivalent                                                                    Circular EC Standard      No. Of                                              Diameter Deviation Open Area                                                                            Apertures/square                           Experiment #                                                                           (mils)   (mils)    (%)    inch                                       ______________________________________                                        15       16.46    10.12     4.55   197                                        16       8.62     9.22      5.34   515                                        17       7.48     8.47      5.34   715                                        18       4.65     2.66      2.31   1125                                       19       4.53     2.65      2.48   1283                                       20       4.00     2.25      2.38   1635                                       21       4.16     2.48      2.53   1519                                       22       6.49     5.59      4.15   806                                        23       6.88     6.18      4.88   856                                        ______________________________________                                    

The data in Table 5 show that the combination of large diameter andsmall diameter orifices (experiments 16, 17, 22, and 23) produce a filmwith larger aperture size and increased open area than films made withsmall diameter orifices alone (experiments 18-21).

FIGS. 22, 23 and 24 are graphs that show the aperture size distributionof films produced in these experiments with a 5 mil diameter orificestrip (Experiment No. 20), a 20 mil diameter orifice strip (ExperimentNo. 15), and the combination of a 20 mil orifice strip followed by a 5mil orifice strip (Experiment No. 16), respectively (see Table 3 above).As seen from these graphs, the apertured films produced with orificestrips of different diameters have aperture sizes that reflect theeffects of various of the individual orifice diameters. The film(Experiment No. 20) produced with only a 5 mil orifice strip hasapertures most of which have a diameter under 10 mils (see FIG. 22). Thefilm (Experiment No. 15) produced by a 20 mil orifice strip only has abroader distribution of aperture diameters, with peak concentrations atapproximately 9 mils and at approximately 23 mils (see FIG. 23). Thefilm (Experiment No. 16) produced by a combination of a 5 mil orificestrip and a 20 mil orifice strip has a distribution of hole diametersthat is primarily concentrated under 12 mils, and has slightconcentration of holes with a diameter of around 23 mils (see FIG. 24).These three graphs indicate that the 5 mil orifices create micro-holesprimarily, that the 20 mil orifices create larger sized holes primarily,and that a combination of 5 mil orifices and 20 mil orifices creates acombination of micro-holes and large sized holes. Comparable data isshown in FIG. 25 which shows aperture size distribution in a sample ofapertured film having micro-holes and large-sized holes in accordancewith the invention that was made on a commercial production line.

                  TABLE 6                                                         ______________________________________                                        Continuous Apertured Film Properties - Strikethrough Time                     Experiment # Strikethrough Time (sec)                                         ______________________________________                                        15           16.3                                                             16           17.6                                                             17           13.5                                                             18           28.8                                                             19           25.6                                                             20           20.2                                                             21           22.9                                                             22           15.8                                                             23           17.10                                                            ______________________________________                                    

The data in Table 6 show that either large diameter orifices alone, orthe combination of large diameter and small diameter orifices(experiments 15, 16, 17, 22 and 23) produce a film with fasterstrikethrough times than films made with small diameter orifices alone(experiments 18-21).

                  TABLE 7                                                         ______________________________________                                        Continuous Apertured Film Properties - Film Stiffness                         Experiment #                                                                           MD Bending Length (mm)                                                                        CD Bending Length (mm)                               ______________________________________                                        15       22.8            6                                                    16       26.3            6.5                                                  17       22.3            6.5                                                  18       27              6.3                                                  19       26.8            5.5                                                  20       26              9.5                                                  21       25.5            8.5                                                  22       23.5            5.8                                                  23       27.30           8.0                                                  comparable                                                                             21.8            14.8                                                 commercial                                                                    product                                                                       ______________________________________                                    

The data indicate that the MD bending length of the films of experiments15-23 is comparable to those of other commercial sanitary napkin plasticcovers, and that the CD bending length of the films is lower thancomparable commercial films. Hence, stiffness and expected comfort ofthe films of the present invention are expected to be comparable orsuperior to that of other commercial apertured films.

Results of additional experimentation are shown in FIG. 26. In theseexperiments, the spacing of the orifices was varied to determine theeffect on film open area. Two water jet manifolds were used in theseexperiments. The first, or upstream, manifold had one orifice strip withtwo rows of orifices on respective sides of the longitudinal center lineof the strip, the two rows of orifices being offset as shown in FIGS.7B-7D, i.e., the offset distance was one-half the intra-row,center-to-center spacing of the orifices. All orifices had a diameter of0.025 inch. The center-to-center spacing of the orifices for eachexperiment was varied as reported in Table 8.

The second, or downstream, manifold had one orifice strip with a singlerow of orifices therein. The orifices each had a diameter of 0.005 inchand were spaced 0.020 inch on a center-to-center basis. Water wassupplied to the first manifold at 150 psig. Water was supplied to thesecond manifold at 1000 psig. The film traveled at 150 ft/min. The drumvacuum was 60 inches water. The following Table 8 indicates the openarea, number of apertures per in², ECD and air permeability for theresulting apertured films.

                  TABLE 8                                                         ______________________________________                                                                        Equivalent                                                                    Circular                                      Film  Large Orifice*                                                                           Open    Number of                                                                            Diameter,                                                                            Air                                    Number                                                                              Spacing, inch                                                                            Area, % Apertures                                                                            inch   Permeability                           ______________________________________                                        24    0.038      13.1    914    0.0099 505                                    25    0.050      12.0    1136   0.0085 476                                    26    0.062      11.2    1151   0.0081 465                                    27    0.075      10.1    1299   0.0072 435                                    ______________________________________                                         *Two rows of 25 mil diameter orifices.                                   

Air permeability was measured per ASTM D737; results are reported inTable 8 in cubic feet per minute per square foot of film. The airpermeabilities of film apertured at 150 psig and 150 ft/min. were 310cfm/sf for the 25-mil diameter orifice strip (only) (0.038 inch spacing)control, which decreased nearly linearly to 245 cfm/sf for the 0.075inch spacing. When the 5-mil diameter strip was added, the airpermeability increased to 505 cfm/sf for the control spacing. There wasa nearly linear decrease with spacing to a value to 435 cfm/sf at 0.075inches. At 150 ft/min., the combination of the large diameter, 25 mildiameter control strip with the 5-mil strip provides about 195 cfm/sfbeyond the measured air permeability of the large hole strip alone. Theabove data indicates that as large orifice spacing increases, fewerlarge-sized holes are produced, and the open area is accordinglyreduced.

Apertured films made according to co-pending Ser. No. 08/417,404 andfilms of the present invention were tested and compared. The films wereprepared on the continuous production line under the followingconditions shown in Table 9.

                  TABLE 9                                                         ______________________________________                                        Apertured Film Preparation And Properties                                     Film made according to                                                                     Ser. No. 08/417,404                                                                         Present Invention                                  Precursor Film                                                                             Exxon EMB-631 Exxon EMB-631                                      ______________________________________                                        Forming Member Pattern                                                                     sinusoidal (12 rails/in.)                                                                   sinusoidal (12 rails/in.)                          Number of Orifice Strips                                                                    3             2                                                 Orifice Strip # 1 Pressure                                                                 875           150                                                (psig)                                                                        Orifice Strip # 2 Pressure                                                                 875           1000                                               (psig)                                                                        Orifice Strip # 3 Pressure                                                                 875                                                              (psig)                                                                        Orifice ID   a/a/a         d/a                                                Orifice size (mils)                                                                        5/5/5         20/5                                               Water Temperature                                                                          158° F.                                                                              160° F.                                     Line Speed (ft./min.)                                                                      150           150                                                Surfactant Treatment                                                                       Tween 20      Tween 20                                           ______________________________________                                    

Sanitary napkins comprising a cover, an absorbent core and a backsheetwere prepared using the apertured films of Table 10 as coverstockmaterials. Two different napkin designs were constructed and tested forstrikethrough and rewet using synthetic menstrual fluid. Syntheticmenstrual fluid was prepared dissolving 0.15% polyacrylamide in isotonicphosphate buffer. Approximately 0.3% Germaben was added to preventbacterial growth. The pH of the solution was measured as 7.4, and theviscosity at 30 centipoise at one radian per second. Results are shownin Tables 11 and 12 below.

                  TABLE 10                                                        ______________________________________                                        Strikethrough And Rewet Of Napkins Made With Apertured Films                  Napkin Design #1                                                              Film made according to                                                                       Ser. No. 08/417,404                                                                        Present Invention                                 ______________________________________                                        5 cc strikethrough time (sec)                                                                68           62                                                Rewet (g)      0.04         0.02                                              ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        Strikethrough And Rewet Of Napkins Made With Apertured Films                  Napkin Design #2                                                              Film made according to                                                                       Ser. No. 08/417,404                                                                        Present Invention                                 ______________________________________                                        5 cc strikethrough time (sec)                                                                39           39                                                Rewet (g)      0.11         0.05                                              ______________________________________                                    

The data in Table 10 and Table 11 show strikethrough time and rewetabsorption. The strikethrough time refers to the time elapsed forabsorption of 5 cc of synthetic menstrual fluid, with a lower time beingdesirable. Rewet absorption refers to the amount of fluid that can beabsorbed in a filter paper that is placed in contact with a sanitarynapkin that has absorbed 5 cc of fluid in the strikethrough test, with alower amount of rewet being desirable.

The data demonstrate that the larger open area and aperture size of thefilms of the present invention give rise to at least equal or fasterstrikethrough times than the prior art films. However, even though theimproved films of the present invention have larger open area and largeraverage aperture size than the prior art films, the napkins made withthe films of the present invention have unexpectedly lower rewet valuesrelative to prior art films.

Another test used to measure the rate of transport of menstrual fluidthrough the apertured film is the "Drop Test". Comparative data for thefilms of the present invention versus prior art films are shown in Table12 below.

                  TABLE 12                                                        ______________________________________                                        Drop Test Data For Apertured Films On Napkin Design #1                        Film Made According To                                                                       Ser. No. 08/417,404                                                                        Present Invention                                 ______________________________________                                        Absorption Time (sec) (0°)                                                            27           8                                                 Absorption Time (sec)                                                                        Drop rolled off                                                                            17                                                (45° transverse tilt)                                                  ______________________________________                                    

The data in Table 12 refers to the time required for absorption of adrop of synthetic menstrual fluid, with a lower time being desirable. Inthe first test, the film was level. In the second test, the film wastilted to an angle of 45°. The data further illustrate the superiorfluid transport properties of films of the present invention relative toprior art films.

Apertured plastic films made according to the present invention exhibitthe following characteristics: tactile softness; textile-like look andfeel; low film stiffness as described in Table 7; aperturing patterns,open areas, and pore sizes ranges as described in Table 5 and FIGS.23-26; low basis weight (≦0.7 oz/yd²); and film/air/synthetic menstrualfluid contact angles on both sides of the film of ≦70°.

The apertured film of the present invention, with surfactant treatment,offers overall comparable fluid penetration rate (as measured by 5 ccsynthetic menstrual fluid strikethrough times--test method described inco-pending patent application Ser. No. 08/417,404 U.S. Pat. No.5,567,376 ), which is improved over non-surfactant-treated films byapproximately 34% in either a pulp absorbent core construction or a peatmoss based absorbent construction.

What is claimed is:
 1. A method for forming an apertured film from astretchable thermoplastic polymeric material comprising:a) providing astarting film comprising said stretchable thermoplastic polymericmaterial having an upper surface and a lower surface; b) providing abacking member comprising localized support regions for supporting saidstarting film, recessed zones into which the film may be deformed by theapplication thereto of fluid forces; and means for allowing said appliedfluid to be transported away from said backing member; c) supportingsaid starting film on said backing member with portions of the lowersurface of said film being in contact with the support regions of saidbacking member and with the upper surface of said film facing away fromsaid backing member; d) forming irregular size micro-holes and largesized holes in said starting film by directing a fluid in the form ofsubstantially non-diverging, columnar streams from at least two sets oforifices against the upper surface of said starting film in a zone ofcontact to cause said starting film to stretch between said backingmember localized support regions over said recessed zones, the orificesof the first set having a diameter greater than ten mils and the fluidsupplied thereto having a pressure less than 500 psig. to cause saidstarting film to rupture into a multiplicity of said large sized holesin said starting film between said localized support regions, theorifices of the second set having a diameter less than or equal to tenmils and the fluid supplied thereto having a pressure of at least 500psig., to cause said starting film to rupture into a multiplicity ofsaid micro-holes in said starting film between said localized supportregions; e) moving said film from said contact zone; and f) removingsaid now-apertured film from said backing member.
 2. A method of formingan apertured film from a stretchable thermoplastic polymeric material inaccordance with claim 1 wherein said first set of orifices have adiameter in the range of about 10 mil to about 30 mils.
 3. A method offorming an apertured film from a stretchable thermoplastic polymericmaterial in accordance with claim 1 wherein said second set of orificeshave a diameter in the range of about 1 mils to about 10 mils.
 4. Amethod of forming an apertured film from a stretchable thermoplasticpolymeric material in accordance with claim 1 wherein said first set oforifices have a diameter in the range of about 15 mils to about 35 mils.5. A method of forming an apertured film from a stretchablethermoplastic polymeric material in accordance with claim 1 wherein saidsecond set of orifices have a diameter in the range of about 3 mils toabout 7 mils.
 6. A method of forming an apertured film from astretchable thermoplastic polymeric material in accordance with claim 1wherein said fluid emitted from said first set of orifices has apressure in the range of about 100 psig to about 500 psig.
 7. A methodof forming an apertured film from a stretchable thermoplastic polymericmaterial in accordance with claim 1 wherein said fluid emitted from saidsecond set of orifices has a pressure in the range of about 500 psig toabout 2000 psig.
 8. A method of forming an apertured film from astretchable thermoplastic polymeric material in accordance with claim 1wherein said fluid emitted from said first set of orifices has apressure in the range of about 125 psig to about 200 psig.
 9. A methodof forming an apertured film from a stretchable thermoplastic polymericmaterial in accordance with claim 1 wherein said fluid emitted from saidsecond set of orifices has a pressure in the range of about 800 psig toabout 1500 psig.
 10. A method of forming an apertured film from astretchable thermoplastic polymeric material in accordance with claim 1including the further step of providing a third set of orifices, saidthird set of orifices havinga diameter less than or equal to about tenmils, the fluid supplied thereto having a pressure of at least 500 psig.11. A method of forming an apertured film from a stretchablethermoplastic polymeric material in accordance with claim 10 whereinsaid third set of orifices have a diameter in the range of about 1 milsto about 10 mils.
 12. A method of forming an apertured film from astretchable thermoplastic polymeric material in accordance with claim 10wherein said third set of orifices have a diameter in the range of about3 mils to about 7 mils.
 13. A method of forming an apertured film from astretchable thermoplastic polymeric material in accordance with claim 10wherein said fluid supplied to said third set of orifices has a pressurein the range of about 500 psig to about 3000 psig.
 14. A method offorming an apertured film from a stretchable thermoplastic polymericmaterial in accordance with claim 10 wherein said fluid emitted fromsaid third set of orifices has a pressure in the range of about 800 psigto about 1500 psig.
 15. A method of forming an apertured film from astretchable thermoplastic polymeric material in accordance with claim 1wherein said micro-holes have an average EHD of about 1 mil to about 7mils.
 16. A method of forming an apertured film from a stretchablethermoplastic polymeric material in accordance with claim 1 wherein saidmicro-holes have an average EHD of about 2 mils to about 5 mils.
 17. Amethod of forming an apertured film from a stretchable thermoplasticpolymeric material in accordance with claim 1 wherein said large sizedholes have an average EHD of about 7 mils to about 30 mils.
 18. A methodof forming an apertured film from a stretchable thermoplastic polymericmaterial in accordance with claim 1 wherein the fluid from the first setof orifices is directed against the upper surface of said starting filmprior to directing the fluid from the second set of orifices.
 19. Amethod of forming an apertured film from a stretchable thermoplasticpolymeric material in accordance with claim 1 wherein said micro-holesare defined by fibrils.
 20. A method of forming an apertured film from astretchable thermoplastic polymeric material in accordance with claim 1wherein said large sized holes are defined by fibrils.
 21. A method forforming an apertured film from a stretchable thermoplastic polymericmaterial comprising:a) providing a starting film comprising saidstretchable thermoplastic polymeric material and having an upper surfaceand a lower surface; b) providing a backing member comprising localizedsupport regions for supporting said starting film, recessed zones intowhich the film may be deformed by the application thereto of fluidforces, and means for allowing said applied fluid to be transported awayfrom said backing member, c) a supporting said starting film on saidbacking member with portions of the lower surface of said film being incontact with the support regions of said backing member and with theupper surface of said film facing away from said backing member; d)forming irregular large sized holes in said starting film by directing afluid in the form of substantially non-diverging, columnar streams froma first set of orifices against the upper surface of said starting filmin a zone of contact to cause said starting film to stretch between saidbacking member localized support regions over said recessed zones, saidorifices in said first set having a diameter greater than or equal toten mils and the fluid supplied thereto causing said starting film torupture into a multiplicity of said large sized holes in said startingfilm between said localized support regions;forming irregular sizemicro-holes in said starting film by directing a fluid in the form ofsubstantially non-diverging, columnar streams from a second set oforifices against the upper surface of said starting film in a zone ofcontact to cause said starting film to stretch between said backingmember localized support regions over said recessed zones, said orificesin said second set having a diameter less than or equal to ten mils andthe fluid emitted therefrom causing said starting film to rupture into amultiplicity of said micro-holes in said starting film between saidlocalized support regions, said micro-holes being defined by fibrils ofsaid thermoplastic material; e) moving said film from said contact zone;and f) removing said now-apertured film from said backing member.
 22. Amethod for forming an apertured film from a stretchable thermoplasticpolymeric material comprising:a) providing an embossed starting filmcomprising said stretchable thermoplastic polymeric material having anupper surface and a lower surface; b) providing a backing membercomprising localized support regions for supporting said starting film,recessed zones into which the film may be deformed by the applicationthereto of fluid forces; and means for allowing said applied fluid to betransported away from said backing member; c) supporting said startingfilm on said backing member with portions of the lower surface of saidfilm being in contact with the support regions of said backing memberand with the upper surface of said film facing away from said backingmember; d) forming irregular size micro-holes and large sized holes insaid starting film by directing a fluid in the form of substantiallynon-diverging, columnar streams from at least two sets of orificesagainst the upper surface of said starting film in a zone of contact tocause said starting film to stretch between said backing memberlocalized support regions over said recessed zones, the orifices of thefirst set having a diameter greater than ten mils and the fluid suppliedthereto having a pressure less than 500 psig. to cause said startingfilm to rupture into a multiplicity of said large sized holes in saidstarting film between said localized support regions, the orifices ofthe second set having a diameter less than or equal to ten mils and thefluid supplied thereto having a pressure of at least 500 psig., to causesaid starting film to rupture into a multiplicity of said micro-holes insaid starting film between said localized support regions; e) movingsaid film from said contact zone; and f) removing said now-aperturedfilm from said backing member.
 23. A method of forming an apertured filmin accordance with claim 22, including providing said embossed startingfilm with corona discharge treatment on one side thereof.
 24. A methodof forming an apertured film in accordance with claim 22 includingapplying a surface active agent to one side of said apertured film.